Stencil duplicating machines



Jan. 28, 1958 A. G. R. GATES STENCIL DUPLICATING MACHINES 3 Sheets-Sheet 1 Filed Dec. 14, 1953 lNl E/VTOE AL BERT G, 9. GA 755- ATTORNEY 1958 'A. s. R. GATES STENCIL DUPLICATING MACHINES 5 Sheecs-Sheec 2 Filed Dec. 14, 1955 5am 195$ A. e. RQ'GATES STENCIL DUPLICATING MACHINES 3 Sheets-Sheet 3 Filed Dec. 14, 1953 nw/Bvm/Q ALBERT 6. 64 5 Uni S tes Patent STENCIL DUPLICATING MACHINES Albert G. R. Gates, Edmonton,

Gestetner Limited, Tottenham, of Great Britain England, assignor to England, a corporation In stencil duplicating machines, such as for ofiice use, there is provided a pressure roller movable towards and away from the cylinder of the machine in synchronism with the paper fed whereby when a sheet is advanced for duplicating the roller is raised to press the sheet against the stencil which is wrapped round the cylinder. The pressure roller is actuated from the driving motor or handle through the intermediary of a cam and cam follower, the pressure roller, being raised and lowered as each sheet is fed through the machine. With increase in the speed of operation of the machine there is a tendency, beyond a certain speed of operation, for the cam to hit the cam follower with such force that the follower moves away from the cam and the pressure roller is thrown up against the cylinder in advance of the travel of the cam. After the pressure roller has hit the cylinder it descends again until further revolution of the cam causes the pressure roller to contact the cylinder again. The pressure roller therefore bounces against the cylinder with the result that undesirable vibration is set up and the quality of the copies obtained is impaired.

It is the object of the present invention accurately to controlthe movement of the roller as it is raised against the cylinder.

Another object of the invention is to ensure that when the pressure roller is brought against the cylinder the contact thus established is continuously maintained during the operation of duplicating.

It is a further object of the invention positively to control the lifting movement of the pressure roller while permitting the roller to fall away from the cylinder on completion of the duplicating operation.

Yet a further object of the invention is to enable, while ensuring positive control of the lifting movement of the pressure roller, that the instant at which the lifting movement commences shall be variable and the lowering movement shall always take place at the same instant.

This and other objects of the invention will be better understood from the following description of the duplicating machine in accordance with the invention. The description of the machine is made with reference to the accompanying drawings of which:

Figure 1 is an end view of a part of a duplicating machine illustrating the mechanism for raising the pressure roller,

Figure 2 is a view in the direction of the arrow II of Figure l and Figure 3 is a section on the line IIIIII of Figure 1.

Referring to Figures 1 and 2, the duplicating machine comprises side frames 5 between which are rotatably mounted an upper cylinder 6 and a lower cylinder 7 around which passes a silk screen 8 to which a stencil may be attached in well known manner. The cylinders 6 and 7 are rotated by the handle 9 which drives gear wheel 10 meshing with a pinion 11 carried on the spindle of cylinder 7. The pressure roller 12 is supported between a pair of arms 13 secured to a shaft 14 pivotally 2,821,129 Patented J an. 28, 1958 carried by brackets 15 (Figure 2) and adjustable, as later described, to raise the roller 12 to engage the stencil on the cylinder 7. The present invention is concerned with the mechanism for actuating the pressure roller 12. The pinion 11 meshes with a gear 16 which drives a gear 17 on a shaft 18. Gear 17 is drivingly connected with a cam 19 as described in the specification of copending appliction Serial No. 398,164, now U. S. Patent No. 2,778,299, so that with rotation of the handle 9 cam 19 is rotated with the gear 17. A pair of cam followers 20, 21 are adapted to engage the opposite sides of the cam 19, the followers being secured to a carrier plate 22 which is slidably mounted in guide ways 23 projecting from a member 25 supported on the shaft 18 for angular adjustment as later described.

The plate 22 is formed with an arcuate slot 26 which receives a pin 27 carried by lever 28 of a lever system connecting the slider plate 22 with the pressure roller. The lever 28 is pivotally supported at 29 and is integral with a second lever 30, the levers 28 and 30 being spaced apart to accommodate the gear wheel 17 therebetween as clearly shown in Figure 1. Lever 30 carries a block 31 coupled to a lever 32 by a connecting rod 33, lever 32 being mounted on the shaft 14.

Rotation of the cam 19 will therefore slide the carrier plate 22 to and fro along the guide ways 23, movement of the plate 22 being transmitted by the levers 28, 30 to the shaft 14 and hence to the pressure roller 12 so as to raise and lower it. The shape of the cam 19 and the sparing of the followers 20, 21 is such that when the cam is moved through annular positions such that the pressure roller 12 is being raised or is being maintained in contact with the cylinder 7, the followers 20, 21 closely engage opposite sides of the cam. This is illustrated in Figs. 2 and 3 where the cam 19 is shown in the position corresponding to the position of maximum lift of the pressure roller. On the other hand, when the cam 19 moves through angular positions such that the pressure roller 12 is lowered, the followers 20, 21 no longer closely engage opposite sides of the cam. It will be appreciated that this construction ensures that when the cam is in the position shown in Figs. 2 and 3 it accurately and positively controls the position of the plate 22 since its opposite sides are engaged by the followers 2t), 21 at this time. Rebound of the pressure roller as a result of the cam hitting the followers is therefore prevented.

The gear wheel 17 carries a part circular support 35 (Figure 2) of constant curvature corresponding to the maximum lift of the cam 19 and the lever 30 carries a roller 36 to engage the support 35. It is arranged that when the follower 20 is displaced to its maximum extent by the cam 19 the roller 36 is displaced to permit the support 35 to pass beneath it. The follower 20 disengages the cam 19 before the roller 36 disengages support 35. After the follower 20 has disengaged the cam 19 the pressure roller 12 will be held in engagement with the cylinder 7 by the support 35 and the pressure roller will be permitted to fall away from the cylinder when the roller 36 drops off the end of the support 35. The support 35 being carried by the gear wheel 17 is in fixed relation to the stencil and therefore the instant at which the pressure roller 12 disengages the stencil is always the same. However, it is desirable that the instant at which the pressure roller engages the stencil shall be varied and to this end the member 25 is manually adjustable by a, lever system generally indicated at 40 and having a member 41 formed with a slide 42 to receive a pin 43 car-- ried by member 25. As the member 25 is angularly adjusted by the lever system 40 the guides 23 are rotated and carrying the plate 22 angularly adjust the followers.

3 20,21 in relationto-thq qan 1 19 thereby varying the extent at which "the cam acts to raise the pressure roller 12 against cylinder 7. The arcuate slide 26 permits of angular adjustment of the plate 22 in relation to pin 27 as described.

The connecting rod 33 carriesa spring, 45 which is adapted to apply the amount of pressure needed between the cylinder and the pressureroller to print a good copy. A spring 4 6 lying between the block 31 and an abutment 47 assists in the return (i. e. lowering) movement of the pressure roller 12.. The weight of the latter also acts to return the roller.

With thearrangement described it willbe appreciated that the raising movement of the roller 12 is positively. controlled so that the roller is incapable of bouncing against the cylinder since the cam 19 acts positively to adjust the plate 22 while. raising the roller 12. When the rollerhas been raised it is maintained in contact with the cylinder by the support 35. Furthermore, the provision of a pin 27 to slide in the arcuate slide 26 ensures that the movement of the plate 22 is accurately applied to thelever system connecting the plate and the shaft 14.

With the arrangement described the instant at which the roller 12 engages cylinder 7 is variable while the instant at which it disengages the cylinder is constant as is well known in stencil duplicating machines.

Reference to the pressure roller 12 engaging the stencil or the cylinder 7 has been made only as a matter of con venience in description. It is to be understood that the roller .at no time engages the stencil or the cylinder but a sheet of paper fed into the machine against the stencil wrapped around the cylinder 7.

I claim:

1. A stencil duplicatingmachine comprising a frame, a cylinder rotatably mounted in the frame and carrying the stencil, a pressure roller, a support for the pressure roller whereby the latter is movable towards the cylinder to apply a sheet of paper fed into the machine against the stencil, a cam, a carrier, a pair of cam followers mounted on said carrier, said followers engaging substan-.

tially oppositesides of the cam while the cam is moving through a predetermined angular range whereby the cam positively controls the position of the carrier while moving through said angular range, a mechanical driving connection between said carrier and the pressure roller where-. by the roller is advanced towards the cylinder when the,

cam movesthrough said angular range, and a common means for driving the cylinder and the cam.

2. A stencil duplicating machine comprising a frame, a cylinder rotatably mounted in the frame and carrying the stencil, a pressure roller, a support for the pressure roller whereby the roller is movable towards the cylinder to apply a sheet of paper fed to the machine to the stencil, a cam, a member rotatably driven with the cam, a part circular support on said rotary member of constant curvature corresponding to the maximum lift of the cam, a pair of followers engaging opposite sides of the cam, a common carrier for said followers, a mechanical driving connection between the carrier and the pressure roller whereby the cam advances the roller to the cylinder, .a roller engageable with said part circular support after said cam follower has been raised to its maximum extent by its cam, a mechanical connection between said supportengaging roller and the pressure roller to hold the pressure roller against said paper sheet while said roller is on said support and common means for driving the cylinder and thecam. V

3. A stencil-duplicating machine as claimed in claim 2 inwhich the rotary member carried by said part-circular support-is positively driven from the cylinder drivingmeans so that the instant of disengagement of the roller .from the paper sheet is constant and the carrier for thefollowers is angularly adjustable so that the instant at whichthe roller engages the paper sheet is variable.

4. A stencil duplicating machine as claimed inclaim 2 whereina common mechanical connection is provided between the carrier and between the support-engaging rollerand the pressure roller.

5. A stencil duplicating machine as claimed in claim 2 wherein the carrier comprises a plate slidably supported between guides onan angularly adjustable member, said carrier plate being slid by said cam in one direction and returned under the weight of the pressure roller.

6. A stencil duplicating machine as calimed in claim 4 wherein the mechanical driving connection comprises a lever system. of which one lever is driven bythe slidable carrier plate, said lever having a pin to enter an arcuate slot in said plate, and another lever carries said roller, said pair of rollers being coupled together for common movement.

References Cited in the file of this patent UNITED STATES PATENTS 1,237,820 Rogers Aug. 21, 1917 2,198,728 Horii Apr. 30, 1940 

